Gorgonopsia

Gorgonopsians Temporal range: Middle Permian-Late Permian, 265–252 Ma PreЄ Є O S D C P T J K Pg N
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Skeleton of Sauroctonus parringtoni
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Clade:	Synapsida
Order:	Therapsida
Suborder:	†Gorgonopsia Seeley, 1895
Family:	†Gorgonopsidae Lydekker, 1890
Genera
See below

Gorgonopsia ("Gorgon face") is an extinct suborder of therapsid synapsids. Like other therapsids, gorgonopsians (or gorgonopsids) were at one time called "mammal-like reptiles" as well as "stem mammals".

Description

Their mammalian specializations include differentiated (heterodont) tooth shape, a fully developed temporal fenestra, pillar-like rear legs, a vaulted palate that may have facilitated breathing while holding the prey, and incipiently developed ear bones. Gorgonopsians are a part of a group of therapsids called theriodonts, which includes mammals. They were among the largest carnivores of the late Permian. The largest known, Inostrancevia, was the size of a large bear with a 45 cm long skull, and 12 cm long saber-like teeth (clearly an adaptation to being a carnivore). They likely did not have a full pelage, but whether they had bristles, scales or naked skin is unknown. They possibly had a combination of all of them, as some mammals still do. Like most therapsids, they are assumed to have been terrestrial, and this is supported both by their morphology and bone microanatomy.

Evolutionary history

Gorgonopsians are theriodonts, a major group of therapsids that included the ancestors of mammals. They evolved in the Middle Permian, from a reptile-like therapsid that also lived in that period. The early gorgonopsians were small, being no larger than a dog. The extinction of dinocephalians (which dominated the Middle Permian world) led to gorgonopsids becoming the apex predators of the Late Permian. Some had approached the size of a rhinoceros, such as Inostrancevia, the largest gorgonopsian. A nearly complete fossil of Rubidgea has been found in South Africa. The Gorgonopsia became extinct at the end of the Permian period, being the only theriodont line to be terminated by this mass extinction.

Classification

The gorgonopsians are one of the three groups of theriodonts (the other two were the therocephalians, and the cynodonts). Theriodonts are related to the herbivorous Anomodontia. Gorgonopsia includes three subfamilies, the Gorgonopsinae, Rubidgeinae and Inostranceviinae, plus a larger number of genera that have not been placed in any of these groups. A total of 25 genera and 41 species, with the genera described most completely being Dinogorgon, Inostrancevia and Rubidgea.

The most comprehensive review of the group is by Sigogneau-Russell, 1989.

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Lycaenops

Gorgonops

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Arctops

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Sauroctonus

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Inostrancevia

• Order Therapsida
• SUBORDER GORGONOPSIA
  • Family Gorgonopsidae
    • Aelurognathus
    • Aelurosaurus
    • Aloposaurus
    • Arctognathus
    • Arctops
    • Broomisaurus
    • Cephalicustriodus
    • Cerdorhinus
    • Clelandina
    • Cyonosaurus
    • Dinogorgon
    • Eoarctops
    • Galesuchus
    • Leontocephalus
    • Lycaenops
    • Paragalerhinus
    • Scylacognathus
    • Sycosaurus
    • Viatkogorgon
    • Subfamily Gorgonopsinae
      • Gorgonops
      • Sauroctonus
      • Scylacops
    • Subfamily Inostranceviinae
      • Inostrancevia
      • Pravoslavlevia
    • Subfamily Rubidgeinae
      • Broomicephalus
      • Leogorgon
      • Prorubidgea
      • Rubidgea

Gebauer (2007) conducted a phylogenetic analysis of gorgonopsians. She did not consider Gorgonopsia and Gorgonopsidae equivalent, and placed only species with autapomorphies, or characteristics unique to those species, in Gorgonopsidae. Aloposaurus, Cyonosaurus, and Aelurosaurus were placed outside Gorgonopsidae as basal gorgonopsids because they did not have autapomorphies. Below is a cladogram from the phylogenetic analysis of Gebauer (2007):

Gorgonopsia	Aloposaurus Cyonosaurus Aelurosaurus Gorgonopsidae Scylacognathus Eoarctops Gorgonops Njalila Lycaenops Arctognathus Inostrancevia Rubidgeinae Aelurognathus Rubidgea Sycosaurus Clelandina

See also

• Evolution of mammals
• Therocephalia

Further reading

• Bakker, R.T. (1986), The Dinosaur Heresies, Kensington Publishing Corp.
• Cox, B. and Savage, R.J.G. and Gardiner, B. and Harrison, C. and Palmer, D. (1988) The Marshall illustrated encyclopedia of dinosaurs & prehistoric animals, 2nd Edition, Marshall Publishing.
• Fenton, C.L. and Fenton, M.A. (1958) The Fossil Book, Doubleday Publishing.
• Hore, P.M. (2005), The Dinosaur Age, Issue #18. National Dinosaur Museum.
• Sigogneau-Russell, D., 1989, "Theriodontia I - Phthinosuchia, Biarmosuchia, Eotitanosuchia, Gorgonopsia" Part 17 B I, Encyclopedia of Paleoherpetology, Gustav Fischer Verlag, Stuttgart and New York.
• Ward, P.D. (2004), Gorgon, Viking Penguin.
• Gebauer (2007), Phylogeny and Evolution of the Gorgonopsia with a Special Reference to the Skull and Skeleton of GPIT/RE/7113 (‘Aelurognathus?’ parringtoni). Ph.D. Dissertation, Tübingen University.